James Francis Thaddeus O'Connor (November 10, 1886 – September 28, 1949) was a United States federal judge.
Born in Grand Forks, North Dakota, O'Connor received an A.B. from the University of North Dakota in 1907, an LL.B. from the University of North Dakota in 1908, an LL.B. from Yale Law School in 1909, and an M.A. from Yale University in 1910. He was an Instructor of Rhetoric at Yale University from 1909 to 1912. He was in private practice in Grand Forks, North Dakota from 1912 to 1925, and in Los Angeles, California from 1925 to 1933.
O'Connor was appointed Comptroller of the Currency by President Franklin D. Roosevelt in 1933, during the worst financial crisis in U.S. history, the Great Depression. To O'Connor fell the tremendous task of disposing of the assets of national banks that were not allowed to reopen after the banking holiday, and terminating receiverships of national banks. During his tenure, the Federal Deposit Insurance Corporation was established. Beginning in 1935, national bank notes were withdrawn from circulation. In 1936, O'Connor, as Comptroller, informed banks that they could not hold bonds that were below investment grade as determined by a handful of rating agencies. O'Connor resigned the Comptroller of the Currency position in April of 1938 in order to campaign for the California Democratic gubernatorial nomination. Unsuccessful in this bid, he returned to private practice in Los Angeles.
With O'Connor's resignation in April of 1938, an Acting Comptroller of the Currency held the Office until September of 1938, when the next Comptroller of the Currency took Office. That Acting Comptroller of the Currency was the then Deputy Comptroller of the Currency, Marshall R. Diggs.
On August 28, 1940, O'Connor was nominated by President Roosevelt to a seat as a federal judge on the United States District Court for the Southern District of California vacated by William P. James. O'Connor was confirmed by the United States Senate on September 19, 1940, and received his commission on September 27, 1940. O'Connor's served in that capacity until his death, in Los Angeles, California.